Free online ISMV to DAT converter

What the ISMV format is

ISMV is a fragmented ISO Base Media File Format video container used by Microsoft Smooth Streaming. Microsoft IIS Media Services, Microsoft Expression Encoder, and related streaming workflows create ISMV segments for adaptive delivery rather than ordinary local playback.

An ISMV file commonly contains H.264 video and AAC audio, although the exact codecs depend on the encoding profile. The file may be one segment of a larger presentation and may rely on an associated .ism manifest. A standalone segment can sometimes be decoded directly, but it may not represent a complete program.

What the DAT format is

In the Video category, DAT usually means the MPEG program stream used on Video CDs. A conventional VCD DAT contains MPEG-1 video at a VCD-compatible resolution and MPEG-1 Layer II audio, normally sampled at 44.1 kHz.

The .dat extension is not a complete format specification: some applications use it for other MPEG program streams. For the widest compatibility with VCD-era players, create a compliant MPEG-1 VCD stream rather than merely renaming the ISMV file.

How to actually convert ISMV to DAT

FFmpeg is the most practical desktop tool because it can read fragmented MP4 media and encode the MPEG-1 video and MP2 audio expected by VCD-compatible DAT files.

1. Install FFmpeg and place the source file in a working folder.
2. For a PAL VCD, run:

ffmpeg -i input.ismv -target pal-vcd output.dat

For an NTSC VCD, use:

ffmpeg -i input.ismv -target ntsc-vcd output.dat

These presets set the relevant MPEG-1 video parameters, frame rate, VCD dimensions, bitrate, MPEG audio settings, and program-stream structure. Replace input.ismv with the actual filename; quote the name if it contains spaces.

If the destination only requires an MPEG program stream with a .dat extension and does not require strict VCD compliance, use a less restrictive command:

ffmpeg -i input.ismv -c:v mpeg1video -q:v 2 -c:a mp2 -b:a 192k -ar 44100 -ac 2 -f mpeg output.dat

For a no-install option, the converter on 101convert.com can process the file online for free. Uploading may be unsuitable for confidential footage or large ISMV segments.

Quality, compatibility, and limitations

This conversion normally requires re-encoding because H.264/AAC content in ISMV is not the MPEG-1/MP2 combination expected by a VCD DAT file. Re-encoding reduces quality, and the VCD bitrate and resolution impose a substantial limit even when the source is high definition.

Choose PAL or NTSC according to the target player and source frame rate. PAL VCD uses 352×288 pixels at 25 fps; NTSC VCD uses 352×240 pixels at approximately 29.97 fps. The presets may alter frame rate and duration when the source does not match the selected standard.

If FFmpeg reports missing streams, incomplete fragments, encryption, or an unreadable manifest relationship, the ISMV may be only a partial Smooth Streaming segment or protected media. Obtain the complete, decrypted presentation before conversion. Inspect the result with a media player or FFmpeg; renaming an ISMV file to .dat does not convert its container or codecs.